This invention relates to the field of digital signal processing and particularly to signal processing useful in digital music synthesis and other applications.
Digital music synthesis has attracted increased interest as data processors have undergone new developments which provide increased performance capabilities. Digital music synthesis has many applications such as the synthesis of stringed, reed and other instruments and such as the synthesis of reverberation.
In actual practice, it has been difficult to provide satisfactory models of music instruments, based upon quantitative physical models, which can be practically synthesized on a real-time basis using present-day computers and digital circuitry.
Most traditional musical instruments such as woodwinds and strings, have been simulated by additive synthesis which consists of summing together sinusoidal harmonics of appropriate amplitude, or equivalently by repeatedly reading from a table consisting of one period of a tone (scaled by an "amplitude function") to "play a note." Another method consists of digitally sampling a real musical sound, storing the samples in digital memory, and thereafter playing back the samples under digital control. FM synthesis as described, for example, in U.S. Pat. No. 4,018,121, has also been successful in synthesizing many musical sounds including brasses, woodwinds, bells, gongs, and some strings. A few instruments have been simulated by "subtractive synthesis" which shapes the spectrum of primitive input signals using digital filters.
All of the foregoing methods (with the occasional exception of subtractive synthesis) have the disadvantage of not being closely related to the underlying physics of sound production. Physically accurate simulations are expensive to compute when general finite-element modeling techniques are used.
In accordance with the above background, there is a need for techniques for synthesizing strings, winds, and other musical instruments including reverberators in a manner which is both physically meaningful and computationally efficient. There is a need for the achievement of natural and expressive computer-controlled performance in ways which are readily comprehensible and easy to use.